I have got to be one of the few people who can actually look at that sort of speak and react as if they typed with correct spelling and grammar, probably because I've been able to talk to my friends from college with them talking to me like that, and truthfully? Most of the time it doesn't take half a brain to understand a lot of the things they say to me, so I'm just used to it on both ends.
I really despise the idea of holding someone's typing etiquette against them to the point I'd refuse to get to know them as a person, because that would just make me feel as though I were horribly judgemental and discriminate. I just can't look down upon somebody who types like that. Heck, I'd really feel warm and appreciated knowing that person would take some of their time just to talk to me, so I just really want to get along with them either way. However, I would respond to them without any abbreviations whatsoever, because it wouldn't be like me to respond in the fashion they do.